Über die Temperaturabhängigkeit der 13C-NMR.-Spektren von [5–6-η-(1Z, 5E)-Cyclooctadien]tetracarbonyleisen und (1Z, 5E)-Cyclooctadien

On the Temperature Dependence of the ¹³C-NMR. Spectra of [5-6-η-(1Z,5E)-Cyclooctadien] and of (lZ, 5E)-Cyclooctadiene The activation parameters of the conformational ring inversion process (simultaneous rotation around the C(3), C(4) and C(7), C(8) bonds; cf. Scheme 1) of the title compounds ( 1 and 2 , respectively) have been determined between 275 L and 155 K by a complete line shape analysis of the temperature dependent proton noise-modulated decoupled ¹³C-NMR. spectra of 1 and 2 . The temperature dependence of the rates (k( 1 ) and k( 2 ), respectively) of the inversion process can be described by the following equations (no influence of the solvents was observed; E_a in J/mol): . Further data are given in Tables 1 and 2. The carbonyl groups of the complex 1 show at 180 K , where the ring inversion process is frozen out, a single line at 211 ppm, i. e. the coalescence temperature of the carbonyl groups must be < 180 K .     

Nicht-Berry Pseudorotation beim Carbonylgruppenaustausch von Tetracarbonyl(η-(Z)-cycloalken)eisen-Komplexen

Exchange of Carbonyl Group Sites in Tetracarbonyl(η-(Z)-cycloalkene)iron Complexes via Non-Berry Pseudorotation The tetracarbonyliron complexes of cyclobutene, cyclopentene, 4,4-dimethyl-cyclopentene, 2,5-dihydrofurane, cyclohexen, (Z)-cyclohepten, -octene, -nonene, and -decene were prepared by thermal or photochemical reaction of the corresponding olefins with nonacarbonyldiiron and pentacarbonyliron, respectively. The low-temperature behaviour of the mostly new complexes which can be stored over a longer period only below 250 K and which exhibit four C,O-stretching frequencies in the IR. spectra (cf. Table 2), indicative for a trigonal bipyramidal structure with the olefin ligand in an equatorial position, was studied in CCl₂F₂ by ¹³C-NMR. spectroscopy between 200 and 115 K. In this temperature range all complexed olefin ligands with the exception of (Z)-cyclooctene (cf. [11]) show an averaged C_s-symmetry on the NMR. time scale. About 115 K the tetracarbonyliron group gives rise to three ¹³C-signals in a ratio of 1:1:2 for the complexes of (Z)-cycloheptene, (Z)-cyclodecene and 2,5-dihydrofurane (Cf. Table 3). This is an agreement with the fixed equatorial position of the non-rotating olefin ligands. The complexes of cyclooctene and cyclononene give only two ¹³C-signals in a ratio of 1:1 for the carbonyl groups. The temperature dependence of the signals indicates that in these cases the two axial carbonyl groups exhibit accidentally the same chemical shift. In all cases a complete line shape analysis of the ¹³C-signals of the carbonyl groups could only be accomplished by using two exchange constants (cf. Tables 4 and 5 as well as Fig. 2–5 and Fig. 8). The same is true for the cyclobutene complex, but only one exchange constant could be determined (at 120 K: two ¹³C-signals in a ratio of 1:3 with the beginning of a further coalescence). The cyclopentene and cyclohexene complexes showed only one ¹³C-signal even at 115 K. The observed temperature-dependent line shapes of the ¹³C-signals can be interpreted in terms of a Non-Berry pseudorotation mechanism involving a three site exchange with each of the two diastereotopic axial carbonyl groups and the two equatorial carbonyl groups (for activation parameters see Table 4). The differences in the activation parameters can be explained on steric grounds by assuming a transition state (cf. Fig. 8) similar to the C_3b-structure of tetracarbonyliron which lies about 27 kJmol^?1 above its C_2v-structure (cf. [30]) comparable with the ground state of our complexes with weak d_π(Fe),p_π(Olefin) back bonding. The transition state model implies that the reorganization process involving the axial carbonyl group in exo-position possesses the higher exchange barrier (cf. Fig. 8).     

Einkristallstudien zur Temperaturabhängigkeit der Kristallstruktur von α-Na3Hg

Temperature Dependent Single Crystal Investigations of α-Na₃Hg In contrast to β-Na₃Hg (rhomboedrally distorted Li₃Bi-type) α-Na₃Hg crystallizes in a hitherto poorly understood variant of the Na₃As-type. Based on temperature dependent measurements of poly- and single crystalline samples (?100°C < T < +35°C) we show, that in particular the sodium atoms (Na1) located in the region of the octahedral Hg₆-holes show a pronounced temperature dependent dynamical behaviour. To a lesser extend this is also true for the tetrahedrally coordinated Na-atoms (Na2). With increasing temperature the former ones more and more approach the centers of the opposite triangular faces of mercury atoms, limiting the Hg₆-octahedra along [001]. Occupation of the latter positions by sodium atoms would lead to unusual short interatomic distances d_{Na? Hg}. However before reaching this unreasonable situation α-Na₃Hg decomposes under formation of β-Na₃Hg.     

1H- und 13C-NMR.-Spektren von 6-(p-X-Phenyl)fulvenen. Kurzmitteilung

¹H- and ¹³C-NMR.-spectra of 6-(p-X-phenyl)fulvenes The ¹H- and ¹³C-NMR.-spectra of a series of 6-(p-X-phenyl)fulvenes 3 , measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5-membered ring. Small changes in bond length are observed by comparison of the vicinal ¹H, ¹H-coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).     

Über die optische Reinheit und die Chiralität der enantiomeren α-2H1-Benzylamine

The optical purity and the absolute configuration of (–)-α-²H₁-benzylamine have been determined by NMR. analysis of a mixture of optically pure diastereoisomeric derivatives.     

Über die pH-Abhängigkeit der 31P- und 31C-NMR-Spektren von Cyclohexan-, Cyclohexen- und Benzenphosphonsäuren

About the pH-Dependence of ³¹P and ¹³C NMR Spectra of Cyclohexane-, Cyclohexene-, and Benzenephosphonic Acids ³¹P and ¹³C chemical shifts as well as P? C coupling constants of phosphonic acids are affected by the pH of the investigated solutions. This dependence was measured for aqueous solutions of cyclohexane-, cyclohex-1-ene-, cyclohex-2-ene-, cyclohex-3-ene-, and benzenephosphonic acid. It is shown that the ³¹P chemical shift and various ¹³C chemical shifts are well suited for the determination of pK_a values.     

Über die Darstellung und die Eigenschaften von σ-Organylwolframpentachloriden

Tungsten hexachloride reacts with dimethyl zinc or diphenyl zinc forming green methyl or phenyl tungsten pentachloride. However, tungsten hexachloride is reduced to tungsten tetrachloride on addition of zinc dialkyls with longer alkyl groups. Furthermore, alkyl tungsten pentachlorides can be prepared from tungsten hexachloride and tin tetraalkyls or boron trialkyls.     

Über die Verbindung Sr7Mn4O15 und Beziehungen zur Struktur von Sr2MnO4 und α-SrMnO3

On the Compound Sr₇Mn₄O₁₅ and Structure Relations to Sr₂MnO₄ and α-SrMnO₃ The “compound” hitherto described as a α modification of Sr₂MnO₄ is shown to consist of a mixture of SrO and the new monoclinic compound Sr₇Mn₄O₁₅ crystallizing in the space group P 2₁/c, a = 681.78(6), b = 962.24(8), c = 1038.0(1) pm, β = 91.886(7)°, Z = 2. Up to 0.3 mm long black crystals were grown from prereacted Sr₇Mn₄O₁₅, SrO, and SrCl₂ at 1350°C in a sealed platinum tube under argon. Its structure is related to α-SrMnO₃. It contains layers of cornershared double octahedra [O_2/2OMnO₃MnO₂O_1/2]^7? parallel to (100). Above 100 K the magnetism of Sr₇Mn₄O₁₅ follows the Curie Weiss law with Θ ～ -426 K and a moment μ_eff = 3.62 μ_B corresponding Mn⁴⁺.     

Über die Stereospezifität der α-Alkylierung von β-Hydroxycarbonsäureestern. Vorläufige Mitteilung

About the Stereospecific α-Alkylation of β-Hydroxyesters It was found, that dianions derived from β-hydroxyesters with lithium diisopropylamide (LDA) at ?50 to ?20° were alkylated stereospecifically (Scheme 1). The stereospecificity was 95–98%, the threo-compound (threo -2, -3 and -4) being the main product. This was proved for threo -2 and -3 by preparing the β-lactones 7 and 8 , respectively, which were pyrolyzed to trans-1, 4-hexadiene (9) and trans-1-phenyl-2-butene (10) , respectively (Scheme 2). Moreover, the acid threo -6 from threo -3 was converted by dimethylformamide-dimethylacetal to cis-1-phenyl-2-butene (11) (s. footnote 6). The alkylation of α-monosubstituted β-hydroxyesters also turned out to be stereospecific. Reduction of 16 and 18 with actively fermenting yeast furnished (+) -17 and (+) -2. respectively (Scheme 4), which were each mixtures of the (2R, 3S)- and the (2S, 3S)-isomers. Alkylation of (+) -17 with allyl bromide yielded after chromatography (2S, 3S) -19 and of (+) -2 with methyl iodide (2R, 3S) -19 , the oxidation of which finally gave (S)-(?) -20 and (R)-(+) -20 , respectively.     

Über die 1,2-Verschiebung von Carbonestergruppen bei der Benzilsäureumlagerung von α,β-Dioxobuttersäure-estern. 25. Mitteilung über Reduktone und Tricarbonylverbindungen [1]

In the benzilic acid type rearrangement of t-butyl α,β-dioxobutyrate (VII) the intact t-butoxycarbonyl group is shifted to the β-carbonyl carbon atom.     

Chemie der Phosphorfluoride. XXXIX. Synthese und Untersuchung der Temperaturabhängigkeit der kernmagnetischen Resonanzspektren von Hexafluorisopropylideniminofluorphosphoranen und Fluorphosphin-Bis(Trifluormethyl)hexafluorisopropylideniminomethylimiden

Chemistry of Phosphorus Fluorides. XXXIX. Synthesis and Investigation of the Dependence of Temperature of the NMR Spectra of Hexafluoroisopropylidence Iminofluorophoranes and Fluorophosphin-Bis(Trifluormethy)hexafluroisopropylidene Imnomethylimides. The title compounds were obtained by the reaction of the lithium salt of hexafluoroisopropylimine with fluorophosphoranes, R_nPF_5?n (n = 0, 1; R = hydrocarbon group). ¹⁹F variable temperature n.m.r. spectra show intermediate rate of intramolecular exchange at phosphorus but apparent fast “isomerisation” at nitrogen. The fluorophosphine imides, on the other hand, show intermediate rates of “isomerisation” at nitrogen in the hexafluoroisopropylidene moiety.     

Über die Natur der Übergangsmetall-Kohlenstoff-σ-Bindung. VIII. Über die Reaktion von 3d-Metallhalogeniden mit Thioanisolyllithium

On the Nature of the Transition Metal Carbon-σ-Bond. VIII. Reaction of 3d-Metal Halides with Thioanisolyl Lithium Reaction of CoBr₂ · 2 THF with PhSCH₂Li/N(CH₂CH₂)₃N (TED) results in the formation of the thiophenolato complex LiCo(SPh)₃ · TED · 3.5 THF (I) with ethylene, propylene, and small amounts of cyclopropane being liberated. The constitution of I follows from the results of the elemental analysis, the effective magnetic moment (μ_eff. = 4.41 B.M.), and the reaction with acids and HgCl₂ to give PhSH and PhSHgCl, respectively. I could also be isolated by comparison synthesis from CoBr₂ · 2 THF and LiSPh/TED. Other 3d-metal halides MX_n · xTHF (M = Ti, V, Mn, Fe, Ni; X = Cl, Br) also react very easily with thioanisolyl lithium to form thiophenolato compounds.     

Über die Darstellung der Tetrachloridazide von Niob und Tantal. Die Kristallstruktur von Tantaltetrachloridazid TaCl4N3

On the Preparation of the Tetrachloride Azides of Niobium and Tantalum. The Crystal Structure of Tantalum Tetrachloride Azide TaCl₄N₃ NbCl₄N₃ and TaCl₄N₃ can be obtained by the reaction of the corresponding pentachlorides with ClN₃ or with NaN₃. TaCl₄N₃ crystallizes in the monoclinic space group P2₁/c: a = 13.63 Å, b = 8.820 Å, c = 13.20 Å, β = 112.07°; z = 8. It is dimeric in solution and in the solid state. The monomers are linked together via the αN atoms of the azide groups to form the centrosymmetric dimers. Two slightly different forms of dimers are found in the crystal structure. They differ in the angle between the azide group und the (Ta? αN)₂ ring. The vibrational spectra of NbCl₄N₃ and TaCl₄N₃ are reported.     

Komplexkatalyse. XXXII. Synthese und Charakterisierung von η3-Allyl-, η3-Crotyl-und η1,η2-Cyclooct-4(Z)-en-1-yl-nickel(II)-bis(brenzcate-chinato)-borat und ihre Eignung als Katalysatoren für die stereospezifische Butadienpolymerisation

Complex Catalysis. XXXII. Synthesis and Characterization of η³-Allyl-, η³-Crotyl-, and η¹,η²-Cyclooct-4(Z)-en-1-yl-nickel(II)-bis(brenzcatechinato)borate and their Suitability as Catalysts for the Stereospecific Butadiene Polymerization By reaction of [(η³-C₃H₅)₂Ni], [(η³-C₄H₇)₂Ni], and [Ni(cycloocta-1,5-diene)₂] with one equivalent bis(brenzcatechinato)boric acid HB(O₂C₆H₄)₂ in ether the complexes given in the title could be synthesized in good yields. The allyl complex [η³-C₃H₅NiB(O₂C₆H₄)₂] reacts with cycloocta-1,5-diene (COD) to give a cationic complex [η³-C₃H₅Ni(COD)]B(O₂C₆H₄)₂ and catalyses the 1,4-trans-polymerization of butadiene with an activity of ca. 150 ml C₄H₆/mol Ni · h and a selectivity of 78% under standard conditions at room temperature.     

Über die säurekatalysierte Umlagerung von β-Jonon-5,6-epoxid

β-Ionone-5,6-epoxide ( 1 ) undergoes acid-catalyzed ring contraction and enlargement, concurrently, by [1, 2]-alkyl shifts, to give the isomeric cyclopentane derivative 6 and the cycloheptafurane derivative 7 . Spectroscopic and chemical evidence for the structures of 6 and 7 is presented.